i was taking flights with CX in asia. sin to hkg, hkg-bkk and then bkk-sin. in the first leg my secretary had given. the travel agent my BA FF number to the travel agent. when i noticed i had it changed to AA where i am platinum. in the next two segments, when i arrived to the counter i was upgraded to bus. and the plane did not seem full (at least bus. was not)

was i just plain lucky? or is there any arrangement between the airlines for top tier FF passengers. i never get these unrequestated upgrades on AA itself.